--- a/taskcluster/taskgraph/transforms/task.py
+++ b/taskcluster/taskgraph/transforms/task.py
@@ -588,17 +588,17 @@ task_description_schema = Schema({
         Optional('rollout-percentage'): int,
     }),
 })
 
 TC_TREEHERDER_SCHEMA_URL = 'https://github.com/taskcluster/taskcluster-treeherder/' \
                            'blob/master/schemas/task-treeherder-config.yml'
 
 
-UNKNOWN_GROUP_NAME = "Treeherder group {} has no name; add it to " + __file__
+UNKNOWN_GROUP_NAME = "Treeherder group {} has no name; add it to taskcluster/ci/config.yml"
 
 V2_ROUTE_TEMPLATES = [
     "index.{trust-domain}.v2.{project}.latest.{product}.{job-name}",
     "index.{trust-domain}.v2.{project}.pushdate.{build_date_long}.{product}.{job-name}",
     "index.{trust-domain}.v2.{project}.pushlog-id.{pushlog_id}.{product}.{job-name}",
     "index.{trust-domain}.v2.{project}.revision.{head_rev}.{product}.{job-name}",
 ]